Managing the Color Temperature for a Light Source Array

ABSTRACT

Providing color management includes receiving measurements of the intensity of colors. A light source generates light beams to yield the colors, where the light beams are generated in accordance to image data to create an image. A target color value is established. A duty cycle sequence operable to control the light source is selected in accordance with the measurements and the target color value. Current levels for currents provided to the light source are selected in accordance with the duty cycle sequence and the target color value.

TECHNICAL FIELD

This invention relates generally to the field of image generation andmore specifically to managing the color temperature for a light sourcearray.

BACKGROUND

Light processing systems often involve directing light towards a displaysuch that an image is produced. One way of effecting such an image isthrough the use of digital micromirror devices (DMD) available fromTexas Instruments. In general, light is shined on a DMD array havingnumerous micromirrors. Each micromirror is selectively controlled toreflect the light towards a particular portion of a display, such as apixel. The angle of a micromirror can be changed to switch a pixel to an“on” or “off” state. The micromirrors can maintain their on or off statefor controlled display times.

The light provided to a DMD array may be generated by a light-emittingdiode (LED) array. The current-to-lumens output of an LED array maychange in response to temperature and as a result of device aging.Accordingly, the color temperature may be managed. Known techniques formanaging the color temperature, however, are not satisfactory in certainsituations. It is generally desirable to have a satisfactory managementof the color temperature in certain situations.

SUMMARY OF THE DISCLOSURE

In accordance with the present invention, disadvantages and problemsassociated with previous techniques for managing color temperature maybe reduced or eliminated.

According to one embodiment of the present invention, providing colormanagement includes receiving measurements of the intensity of colors. Alight source generates light beams to yield the colors, where the lightbeams are generated in accordance to image data to create an image. Atarget color value is established. A duty cycle sequence operable tocontrol the light source is selected in accordance with the measurementsand the target color value. Current levels for currents provided to thelight source are selected in accordance with the duty cycle sequence andthe target color value.

Certain embodiments of the invention may provide one or more technicaladvantages. A technical advantage of one embodiment may be that currentlevels and duty cycle sequences provided to a light source array aresynchronized in order to manage the color temperature or xy location ofthe array. The color management may yield an appropriate colortemperature or xy location while optimizing the lumens output of thelight source array.

Certain embodiments of the invention may include none, some, or all ofthe above technical advantages. One or more other technical advantagesmay be readily apparent to one skilled in the art from the figures,descriptions, and claims included herein.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and itsfeatures and advantages, reference is now made to the followingdescription, taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a block diagram illustrating one embodiment of a system forproviding color management for a light source array; and

FIG. 2 is a flowchart illustrating one embodiment of a method forproviding color management for a light source array.

DETAILED DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention and its advantages are bestunderstood by referring to FIGS. 1 and 2 of the drawings, like numeralsbeing used for like and corresponding parts of the various drawings.

FIG. 1 is a block diagram illustrating one embodiment of a system 10 forproviding color management for a light source array. According to theembodiment, system 10 may synchronize current levels and duty cyclesequences in order to manage the color temperature or xy location of alight source array.

In general, the current level of a current provided to a light sourcearray may be controlled to provide color management. The range in whichthe current level adjustment can provide appropriate color management,however, is limited. Moreover, duty cycle sequences that control theduty cycle for colors may also be used for color management. Typically,only a certain number of sequences are available, however, and switchingabruptly from one sequence to another sequence may yield adiscontinuity.

According to one embodiment, system 10 coordinates duty cycle controland current level control. Duty cycle sequences may be selected in orderto provide a coarse adjustment. A sequence may be selected to maintain acurrent level in the range in which appropriate color managementadjustment may be provided. Once in the range, the current level may beadjusted to provide a fine adjustment.

According to the illustrated embodiment, system 10 includes a dataprocessing unit 20, a color manager 24, an internal sensor 28, and aprojector 36, which includes a light source driver 44, a light source48, and a spatial modulator 52. Projector 36 projects an image on ascreen 40, and external sensor 28 detects the image. In general, colormanager 24 uses image data and control information from data processingunit 20 and measurements from internal sensor 28 and external sensor 42to provide color management for projector 36. Image data may refer todata that is used to generate an image on screen 40. Control informationmay refer to instructions that are used to control components of system10 to process the image data. As an example, a duty cycle sequencecontrols when and how light beams are provided to spatial modulator 52.The sequence may also control when and which elements of a light source48 are turned on and off.

System 10 controls the projection of colors on screen 40 to generate animage. Colors may be defined as (x,y) points of the InternationalCommission on Illumination (CIE) chromaticity diagram. Primary colorsare colors with a controllable intensity. Any suitable primaries may beused. As an example, primaries may include red, green, blue, yellow,cyan, magenta, other primary, or any suitable combination of thepreceding. One or more light elements of light source 48 may be used togenerate a primary.

Primaries may be combined with specific intensities to yield a combinedcolor. The (x,y) point of the combined color may be calculated from the(x,y) points and the intensity of the primaries. Changing the averageintensity of the primaries may yield a combined color at a different(x,y) point.

The average intensity of the primaries may be changed by adjusting thedisplay time, intensity, or both display time and intensity of aprimary. According to one embodiment, light source 48 comprises an LEDarray. The amount of time may be controlled by adjusting the duty cyclesequence of an LED or by adjusting the image data. The intensity may becontrolled by adjusting the current level of the current provided to theLED and the number of active LEDs.

According to the illustrated embodiment, data processing unit 20 mayprovide image data and control information to other components of system10. As an example, data processing unit 20 may provide timing signalsand user controls to color manager 24. Data processing unit 20 may alsoprovide duty cycle sequences selected by color manager 24 to lightsource driver 44.

Color manager 24 provides color management for system 10. Color manager24 may send control information to other components to provide colormanagement. As an example, color manager 24 may provide current controlinformation to light source driver 44 that instructs light source driver44 to provide light source 48 with the selected current levels. Colormanager 24 may also provide sequence control information to dataprocessing unit 20. The sequence control information may includeselected duty cycle sequences for light source driver 44. Color manager24 may use any suitable method to provide color management. An examplemethod is described with reference to FIG. 2.

Internal sensor 28 measures lumens output by the primaries. Internalsensor 28 may include any suitable number of detectors, for example,three or more detectors, each with a filter to restrict the measuredwavelength. The filter characteristics may overlap to allow forwavelength determination based upon the measurements.

Internal sensor 28 may be placed in any suitable location of system 10.As an example, internal sensor 28 may be placed in the light pathbetween light source 48 and spatial modulator 52. As another example,internal sensor 28 may be placed in the off-state light between spatialmodulator 52 and screen 40.

Internal sensor 28 may provide sets of measurements. A first set ofmeasurements may be taken under the same conditions as the calibrationdata. These measurements may be used to allow a correction process totrack the performance of the output of the LED array. A second set ofmeasurements may be taken under varying current levels, for example, anysuitable levels between a maximum LED current level and a minimum LEDcurrent level. The measurements may be recorded in a table that may beupdated. A third set of measurements may be taken at full power tomeasure individual LED strings. The measurements may be used to detect afailure of an LED string. If the lumens output for a string is below anacceptable level, the string may be disabled.

Projector 36 directs light towards screen 40 to generate an image.Projector 36 may comprise any suitable components or combination ofcomponents for directing light towards screen 40. According to theillustrated embodiment, projector 36 may comprise a light source driver44, a light source 48, and a spatial modulator 52.

Light source driver 44 receives image data and control information, andinstructs light source 48 to emit light beams towards spatial modulator52 in accordance with the image data and control information. A “lightbeam” may refer to a beam of light radiation, and may comprise a laserbeam. Example light sources may include semiconductor lasers,light-emitting diodes (LEDs), injection laser diodes (ILDs), verticalcavity surface emitting diodes (VCSELs), an array of light sources,lasers, or any other suitable source that emits light beams. Accordingto one embodiment, light source 48 may comprise an LED array, thatincludes strings of one or more LEDs. The strings may be driven at acommon current level or different current levels.

Spatial modulator 52 spatially modulates light received from lightsource 48, and directs the spatially modulated light beams to screen 40.Spatial modulator 52 may comprise any device capable of selectivelycommunicating at least some light beams to screen 40. Data processingunit 20 may be operable to configure and program spatial modulator 52 toprocess analog signals with digital precision.

According to one embodiment, the modulator comprises a digitalmicromirror device (DMD). A DMD may refer to a digital form of a spatiallight modulator that comprises an electromechanical device including apixel array. The pixel array may comprise an array, such as a 768×1024array, of digital tilting mirrors or baseline binary pixels or mirrors.A binary mirror may tilt by a plus or minus angle of, for example, 10 or12 degrees, for active “on” or “off” positions. A mirror may include anactuator that permits the mirror to tilt. An actuator may comprisehinges mounted on support posts over underlying control circuitry. Thecontrol circuitry provides electrostatic forces that cause each mirrorto selectively tilt.

External sensor 42 measures the intensity of light after the light beamstravel a complete optical path. A complete optical path may includescreen 40 and a path between screen 40 and a viewer. External sensor 42may include any suitable number of detectors, for example, three or moredetectors.

One or more components of system 10 may include appropriate inputdevices, output devices, mass storage media, processors, memory, orother components for receiving, processing, storing, or communicatinginformation according to the operation of system 10. As an example, oneor more components of system 10 may include logic, an interface, memory,other component, or any suitable combination of the preceding. “Logic”may refer to hardware, software, other logic, or any suitablecombination of the preceding. Certain logic may manage the operation ofa device, and may comprise, for example, a field programmable gate array(FPGA) or a digital signal processor (DSP). “Processor” may refer to anysuitable device operable to execute instructions and manipulate data toperform operations.

“Interface” may refer to logic of a device operable to receive input forthe device, send output from the device, perform suitable processing ofthe input or output or both, or any combination of the preceding, andmay comprise one or more ports, conversion software, or both. “Memory”may refer to logic operable to store and facilitate retrieval ofinformation, and may comprise Random Access Memory (RAM), Read OnlyMemory (ROM), a magnetic drive, a disk drive, a Compact Disk (CD) drive,a Digital Video Disk (DVD) drive, removable media storage, any othersuitable data storage medium, or a combination of any of the preceding.

Modifications, additions, or omissions may be made to system 10 withoutdeparting from the scope of the invention. The components of system 10may be integrated or separated according to particular needs. Moreover,the operations of system 10 may be performed by more, fewer, or othermodules. For example, the operations of light source driver 44 and lightsource 48 may be performed by one module, or the operations of colormanager 24 may be performed by more than one module. As used in thisdocument, “each” refers to each member of a set or each member of asubset of a set.

FIG. 2 is a flowchart illustrating one embodiment of a method forproviding color management for a light source array. The method may beused to determine duty cycle sequences that may maintain current levelsin a particular range, and to determine the current levels that mayprovide color management. The method may also be used to alter anidentity matrix that may adjust video data to provide color management.According to the embodiment, the light source is assumed to comprisestable LEDs.

According to the embodiment, internal and external measurements may betaken simultaneously as an average of a number of sample measurements.Internal measurements may be designated using ABC values, and externalmeasurements may be designated using XYZ values. Duty cycle sequencesmay be designated using RGB values. In the example, “[ ]” representsmatrix operations, and “( )” represents element by element operations.Also, “DEF_(GH)” represents D_(GH), E_(GH), and F_(GH).

The method begins at step 100, where calibration is performed. Duringcalibration, internal measurements are correlated with externalmeasurements. Any suitable parameters may be calibrated. As an example,the duty cycle sequences RGB_(DCcal) may be calibrated. As anotherexample, full color parameters may be calibrated. Full color parametersmay include red, green, and blue full color parameters, which may eachinclude external xyY parameters and internal ABC parameters. Red fullcolor parameters may include external parameters xyY_(rcal) and internalparameters ABC_(rcal); green full color parameters may include externalparameters xyY_(gcal) and internal parameters ABC_(gcal); and blue fullcolor parameters may include external parameters xyY_(bcal) and internalparameters ABC_(bcal).

Inputs are received at step 104. Inputs may include target white pointvalues XYZ_(wp) for each white point. Inputs may also includeinformation about the system, for example, available duty cyclesequences and real time duty cycle sequences RGB_(DCrt) Systeminformation may also include a real time current lookup table (LUT) thatassociates values ABC_(xc), x=r, g, and b to current levels. Systeminformation may also include real time red, green, and blue peakparameters ABC_(xrt), x=r, g, and b measured at the maximum currentlevel.

Inputs may also include a p7 matrix. A p7 matrix may be used to adjustthe image data in an enhanced color correction technique. An example p7matrix is described in U.S. Pat. No. 6,594,387, which is herebyincorporated by reference. A p7 matrix may be defined according toEquation (1): $\begin{matrix}{\begin{bmatrix}1 & 0 & 0 & 0 & 1 & 1 & 1 \\0 & 1 & 0 & 1 & 0 & 1 & 1 \\0 & 0 & 1 & 1 & 1 & 0 & 1\end{bmatrix} = {p\quad 7i}} & (1)\end{matrix}$

The method generates output, which may include a next duty cyclesequence RGB_(seq), next current levels RGB_(c), and a next p7 matrixthat may provide color management.

Matrices are accessed at step 108. The matrices may include an externalsystem matrix and an internal system matrix that may be used to generatea full system matrix. The external system matrix may be given byEquation (2): $\begin{matrix}{\begin{bmatrix}X_{r} & X_{g} & X_{b} \\Y_{r} & Y_{g} & Y_{b} \\Z_{r} & Z_{g} & Z_{b}\end{bmatrix}{{where}\text{:}}{X_{wcal} = {X_{rcal} + X_{gcal} + X_{bcal}}}{Y_{wcal} = {Y_{rcal} + Y_{gcal} + Y_{bcal}}}{Z_{wcal} = {{Z_{rcal} + Z_{gcal} + {Z_{bcal}\begin{pmatrix}k_{x} \\k_{y} \\k_{z}\end{pmatrix}}} = {{\begin{bmatrix}x_{rcal} & x_{gcal} & x_{bcal} \\y_{rcal} & y_{gcal} & y_{bcal} \\z_{rcal} & z_{gcal} & z_{bcal}\end{bmatrix}^{- 1}*{\begin{bmatrix}\left( \frac{X_{wcal}}{Y_{wcal}} \right) \\1 \\\left( \frac{z_{wcal}}{Y_{wcal}} \right)\end{bmatrix}\begin{bmatrix}X_{r} & X_{g} & X_{b} \\Y_{r} & Y_{g} & Y_{b} \\Z_{r} & Z_{g} & Z_{b}\end{bmatrix}}} = {\begin{bmatrix}x_{rcal} & x_{gcal} & x_{bcal} \\y_{rcal} & y_{gcal} & y_{bcal} \\z_{rcal} & z_{gcal} & z_{bcal}\end{bmatrix}*\begin{bmatrix}k_{x} & 0 & 0 \\0 & k_{y} & 0 \\0 & 0 & k_{z}\end{bmatrix}}}}}} & (2)\end{matrix}$and i=r, g, b, w_(i), z_(i)=1−x_(i)−y_(i),${X_{i} = {\frac{x_{i}}{y_{i}}Y_{i}}},\quad{{{and}\quad Z_{i}} = {\frac{z_{i}}{y_{i}}{Y_{i}.}}}$

The internal system matrix may be given by Equation (3): $\begin{matrix}{\begin{bmatrix}A_{r} & A_{g} & A_{b} \\B_{r} & B_{g} & B_{b} \\C_{r} & C_{g} & C_{b}\end{bmatrix}{{where}\text{:}}{A_{wcal} = {A_{rcal} + A_{gcal} + A_{bcal}}}{B_{wcal} = {B_{rcal} + B_{gcal} + B_{bcal}}}{C_{wcal} = {{C_{rcal} + C_{gcal} + {C_{bcal}\begin{pmatrix}k_{a} \\k_{b} \\k_{c}\end{pmatrix}}} = {{\begin{bmatrix}a_{rcal} & a_{gcal} & a_{bcal} \\b_{rcal} & b_{gcal} & b_{bcal} \\c_{rcal} & c_{gcal} & c_{bcal}\end{bmatrix}^{- 1}*{\begin{bmatrix}\left( \frac{A_{wcal}}{B_{wcal}} \right) \\1 \\\left( \frac{C_{wcal}}{B_{wcal}} \right)\end{bmatrix}\begin{bmatrix}A_{r} & A_{g} & A_{b} \\B_{r} & B_{g} & B_{b} \\C_{r} & C_{g} & C_{b}\end{bmatrix}}} = {\begin{bmatrix}a_{rcal} & a_{gcal} & a_{bcal} \\b_{rcal} & b_{gcal} & b_{bcal} \\c_{rcal} & c_{gcal} & c_{bcal}\end{bmatrix}*\begin{bmatrix}k_{a} & 0 & 0 \\0 & k_{b} & 0 \\0 & 0 & k_{c}\end{bmatrix}}}}}{and}{{a_{i} = \frac{A_{i}}{A_{i} + B_{i} + C_{i}}},\quad{b_{i} = \frac{B_{i}}{A_{i} + B_{i} + C_{i}}},\quad{{{and}\quad c_{i}} = {\frac{C_{i}}{A_{i} + B_{i} + C_{i}}.}}}} & (3)\end{matrix}$

The internal system matrix and the inverse of the external system matrixmay be multiplied together to create the full system matrix according toEquation (4): $\begin{matrix}{\begin{bmatrix}I_{r} & I_{g} & I_{b} \\J_{r} & J_{g} & J_{b} \\K_{r} & K_{g} & K_{b}\end{bmatrix} = {\begin{bmatrix}A_{r} & A_{g} & A_{b} \\B_{r} & B_{g} & B_{b} \\C_{r} & C_{g} & C_{b}\end{bmatrix}*\begin{bmatrix}X_{r} & X_{g} & X_{b} \\Y_{r} & Y_{g} & Y_{b} \\Z_{r} & Z_{g} & Z_{b}\end{bmatrix}^{- 1}}} & (4)\end{matrix}$

The external and internal values are scaled at step 112. The externalsensor can detect changes in the duty cycles, whereas the internalsensor cannot detect such changes. Accordingly, external values, such asthe target white point values XYZ_(wp), may be scaled by the calibrationduty cycles. Scaling factors XYZ_(sfactor) for white point values XYZmay be calculated according to Equation (5): $\begin{matrix}{\begin{pmatrix}X_{sfactor} \\Y_{sfactor} \\Z_{sfactor}\end{pmatrix} = \frac{\begin{bmatrix}X_{r} & X_{g} & X_{b} \\Y_{r} & Y_{g} & Y_{b} \\Z_{r} & Z_{g} & Z_{b}\end{bmatrix}*\begin{bmatrix}\left( R_{DCcal} \right) \\\left( G_{DCcal} \right) \\\left( B_{DCcal} \right)\end{bmatrix}}{\begin{bmatrix}\left( \frac{X_{wcal}}{Y_{wcal}} \right) \\1 \\\left( \frac{Z_{wcal}}{Y_{wcal}} \right)\end{bmatrix}}} & (5)\end{matrix}$

Scaled white point values XYZ_(scaledwp) may be calculated according toEquation (6): $\begin{matrix}{\begin{pmatrix}X_{scaledwp} \\Y_{scaledwp} \\Z_{scaledwp}\end{pmatrix} = {\begin{pmatrix}X_{wp} \\Y_{wp} \\Z_{wp}\end{pmatrix}*\begin{pmatrix}X_{sfactor} \\Y_{sfactor} \\Z_{sfactor}\end{pmatrix}}} & (6)\end{matrix}$

Steps 116 and 120 are performed to select duty cycle sequences. Thedifference RGB_(%diff1) between target white point values ABC_(wp) andreal time white point values ABC_(rt) is calculated at step 116. Thedifference may be calculated in any suitable manner. According to oneembodiment, the target white point values ABC_(wp) may be determined bycalculating the ABC values for white when the target white point isachieved, and may be calculated according to Equation (7):$\begin{matrix}{\begin{pmatrix}A_{wp} \\B_{wp} \\C_{wp}\end{pmatrix} = {\begin{bmatrix}I_{r} & I_{g} & I_{b} \\J_{r} & J_{g} & J_{b} \\K_{r} & K_{g} & K_{b}\end{bmatrix}*\begin{bmatrix}X_{scaledwp} \\Y_{scaledwp} \\Z_{scaledwp}\end{bmatrix}}} & (7)\end{matrix}$

The values ABC_(wp) may be normalized so that they can be compared toother ABC values, and may be normalized according to Equations (8) toyield normalized target white point values nABC_(wp): $\begin{matrix}{{{n\quad A_{wp}} = \frac{A_{wp}}{A_{wp} + B_{wp} + C_{wp}}}{{n\quad B_{wp}} = \frac{B_{wp}}{A_{wp} + B_{wp} + C_{wp}}}{{n\quad C_{wp}} = \frac{C_{wp}}{A_{wp} + B_{wp} + C_{wp}}}} & (8)\end{matrix}$

The real time white point values ABC_(wrt) may be calculated accordingto Equation (9): $\begin{matrix}{\begin{pmatrix}A_{wrt} \\B_{wrt} \\C_{wrt}\end{pmatrix} = {\begin{bmatrix}A_{rrt} & A_{grt} & A_{brt} \\B_{rrt} & B_{grt} & B_{brt} \\C_{rrt} & C_{grt} & C_{brt}\end{bmatrix}*\begin{bmatrix}R_{D\quad{Crt}} \\G_{D\quad{Crt}} \\B_{D\quad{Crt}}\end{bmatrix}}} & (9)\end{matrix}$

The values ABC_(wrt) may be normalized according to Equations (10) toyield normalized real time white point values nABC_(wrt):$\begin{matrix}{{{n\quad A_{wrt}} = \frac{A_{wrt}}{A_{wrt} + B_{wrt} + C_{wrt}}}{{nB}_{wrt} = \frac{B_{wrt}}{A_{wrt} + B_{wrt} + C_{wrt}}}{{nC}_{wrt} = \frac{C_{wrt}}{A_{wrt} + B_{wrt} + C_{wrt}}}} & (10)\end{matrix}$

The percent differences RGB_(%diff1) between the normalized target whitepoint values ABC_(wp) and the normalized real time white point valuesABC_(wrt) may be calculated according to Equation (11): $\begin{matrix}{\begin{pmatrix}R_{\%\quad{diff}\quad 1} \\G_{\%\quad{diff}\quad 1} \\B_{\%\quad{diff}\quad 1}\end{pmatrix} = \frac{\left( {\begin{pmatrix}{n\quad A_{wp}} \\{n\quad B_{wp}} \\{nC}_{wp}\end{pmatrix} - \begin{pmatrix}{n\quad A_{wrt}} \\{n\quad B_{wrt}} \\{nC}_{wrt}\end{pmatrix}} \right)}{\begin{pmatrix}{n\quad A_{wp}} \\{n\quad B_{wp}} \\{nC}_{wp}\end{pmatrix}}} & (11)\end{matrix}$

Duty cycles that correspond to the difference are established at step120. The duty cycles may be established in any suitable manner.According to one embodiment, next duty cycles RGB_(DC) may be determinedaccording to Equation (12): $\begin{matrix}{\begin{pmatrix}R_{D\quad C} \\G_{D\quad C} \\B_{D\quad C}\end{pmatrix} = {{\begin{pmatrix}R_{DCrt} \\G_{DCrt} \\B_{DCrt}\end{pmatrix}*\begin{pmatrix}R_{\%\quad{diff}\quad 1} \\G_{\%\quad{diff}\quad 1} \\B_{\%\quad{diff}\quad 1}\end{pmatrix}} + \begin{pmatrix}R_{DCrt} \\G_{DCrt} \\B_{DCrt}\end{pmatrix}}} & (12)\end{matrix}$

The duty cycles may be normalized according to Equations (13) to yieldnormalized duty cycles nRGB_(DC): $\begin{matrix}{{{nR}_{D\quad C} = {\frac{R_{D\quad C}}{R_{D\quad C} + G_{D\quad C} + B_{D\quad C}}*100}}{{nG}_{D\quad C} = {\frac{G_{D\quad C}}{R_{D\quad C} + G_{D\quad C} + B_{D\quad C}}*100}}{{nB}_{D\quad C} = {\frac{B_{D\quad C}}{R_{D\quad C} + G_{D\quad C} + B_{D\quad C}}*100}}} & (13)\end{matrix}$An available sequence RGB_(seq) with duty cycles that are closest tonormalized next duty cycles nRGB_(DC) may be selected.

Steps 124 and 128 are performed to select current levels. The percentdifferences RGB_(%diff2) between the target white point values nABC_(wp)and internal white point values nABC_(wseq) at the selected sequence iscalculated at step 124. Internal white point values ABC_(wseq) may becalculated according to Equation (14): $\begin{matrix}{\begin{pmatrix}A_{wseq} \\B_{wseq} \\C_{wseq}\end{pmatrix} = {\begin{bmatrix}A_{rrt} & A_{grt} & A_{brt} \\B_{rrt} & B_{grt} & B_{brt} \\C_{rrt} & C_{grt} & C_{brt}\end{bmatrix}*\begin{bmatrix}R_{seq} \\G_{seq} \\B_{seq}\end{bmatrix}}} & (14)\end{matrix}$

The internal white point values ABC_(wseq) may be normalized accordingto Equations (15) to yield normalized internal white point valuesnABC_(wseq): $\begin{matrix}{{{n\quad A_{wseq}} = \frac{A_{wseq}}{A_{wseq} + B_{wseq} + C_{wseq}}}{{nB}_{wseq} = \frac{B_{wseq}}{A_{wseq} + B_{wseq} + C_{wseq}}}{{nC}_{wseq} = \frac{C_{wseq}}{A_{wseq} + B_{wseq} + C_{wseq}}}} & (15)\end{matrix}$

The difference RGB_(%diff2) may be calculated according to Equation(16): $\begin{matrix}{\begin{pmatrix}R_{\%\quad{diff}\quad 2} \\G_{\%\quad{diff}\quad 2} \\B_{\%\quad{diff}\quad 2}\end{pmatrix} = {\left( \frac{\left( {\begin{pmatrix}{n\quad A_{wp}} \\{n\quad B_{wp}} \\{nC}_{wp}\end{pmatrix} - \begin{pmatrix}{n\quad A_{wseq}} \\{n\quad B_{wseq}} \\{nC}_{wseq}\end{pmatrix}} \right)}{\begin{pmatrix}{n\quad A_{wp}} \\{n\quad B_{wp}} \\{nC}_{wp}\end{pmatrix}} \right) + 1}} & (16)\end{matrix}$

The difference RGB_(%diff2) may be normalized such that the maximumpercent difference is one, and may be normalized according to Equation(17) to yield normalized difference nRGB_(%diff2): $\begin{matrix}{{{nR}_{\%\quad{diff}\quad 2} = \frac{R_{\%\quad{diff}\quad 2}}{\max\left( {R_{\%\quad{diff}\quad 2},G_{\%\quad{diff}\quad 2},B_{\%\quad{diff}\quad 2}} \right)}}{{nG}_{\%\quad{diff}\quad 2} = \frac{G_{\%\quad{diff}\quad 2}}{\max\left( {R_{\%\quad{diff}\quad 2},G_{\%\quad{diff}\quad 2},B_{\%\quad{diff}\quad 2}} \right)}}{{nB}_{\%\quad{diff}\quad 2} = \frac{B_{\%\quad{diff}\quad 2}}{\max\left( {R_{\%\quad{diff}\quad 2},G_{\%\quad{diff}\quad 2},B_{\%\quad{diff}\quad 2}} \right)}}} & (17)\end{matrix}$

The current level that corresponds to the difference RGB_(%diff2) isdetermined at step 128. The current level may be determined in anysuitable manner. According to one embodiment, the red, green, and bluereal time internal sensor ABC values may be scaled by percentdifferences RGB_(%diff2) according to Equation (18) to yield scaledvalues ABC_(xscaled), x=r, g, and b:A _(rscaled) =A _(rrt) *nR _(%diff2)B _(gscaled) =B _(grt) *nG _(%diff2)C _(bscaled) =C _(brt) *nB _(%diff2)  (18)

Current levels corresponding to the difference are established at step128. The current levels may be established by interpolating the currentlookup table to determine interpolated current levels iRGB_(c)corresponding to the scaled values ABC_(xscaled). Current levels RGB_(c)closest to the interpolated current levels iRGB_(c) may be selected.

Steps 132 and 136 are performed to determine a p7 matrix that may beused to adjust image data to provide color management. The differenceRGB_(%diff3) between the target white point values nABC_(wp) andestimated white point values nABC_(wcurr) based on the selected sequenceand current levels is calculated at step 132. The differenceRGB_(%diff3) may be calculated in any suitable manner. According to oneembodiment, the estimated white point values ABC_(wcurr) at the selectedsequence and current levels may be determined according to Equation(19): $\begin{matrix}{\begin{pmatrix}A_{wcurr} \\B_{wcurr} \\C_{wcurr}\end{pmatrix} = {\begin{bmatrix}A_{rcurr} & A_{gcurr} & A_{bcurr} \\B_{rcurr} & B_{gcurr} & B_{bcurr} \\C_{rcurr} & C_{gcurr} & C_{bcurr}\end{bmatrix}*\begin{bmatrix}R_{seq} \\G_{seq} \\B_{seq}\end{bmatrix}}} & (19)\end{matrix}$where ABC_(xcurr), x=r, g, b, represent the ABC values of the internalsensor at the selected current levels. Values ABC_(xcurr) may beestablished by interpolating the current lookup table to determine theABC_(xc) values corresponding to the available current levels.

The estimated white point values ABC_(wcurr) may be normalized accordingto Equation (20) to yield normalized white point values nABC_(wcurr):$\begin{matrix}{{{n\quad A_{wcurr}} = \frac{A_{wcurr}}{A_{wcurr} + B_{wcurr} + C_{wcurr}}}{{nB}_{wcurr} = \frac{B_{wcurr}}{A_{wcurr} + B_{wcurr} + C_{wcurr}}}{{nC}_{wcurr} = \frac{C_{wcurr}}{A_{wcurr} + B_{wcurr} + C_{wcurr}}}} & (20)\end{matrix}$

The difference between the target white point values nABC_(wp) and theestimated white point values nABC_(wcurr) at the selected sequence andcurrent levels may be calculated according to Equation (21):$\begin{matrix}{\begin{pmatrix}R_{\%\quad{diff}\quad 3} \\G_{\%\quad{diff}\quad 3} \\B_{\%\quad{diff}\quad 3}\end{pmatrix} = {\left( \frac{\left( {\begin{pmatrix}{n\quad A_{wp}} \\{nB}_{wp} \\{nC}_{wp}\end{pmatrix} - \begin{pmatrix}{n\quad A_{wcurr}} \\{nB}_{wcurr} \\{nC}_{wcurr}\end{pmatrix}} \right)}{\begin{pmatrix}{n\quad A_{wp}} \\{mB}_{wp} \\{nC}_{wp}\end{pmatrix}} \right) + 1}} & (21)\end{matrix}$

The difference may be normalized according to Equation (22) so that themaximum percent difference is one: $\begin{matrix}{{{nR}_{\%\quad{diff}\quad 3} = \frac{R_{\%\quad{diff}\quad 3}}{\max\left( {R_{\%\quad{diff}\quad 3},G_{\%\quad{diff}\quad 3},B_{\%\quad{diff}\quad 3}} \right)}}{{nG}_{\%\quad{diff}\quad 3} = \frac{G_{\%\quad{diff}\quad 3}}{\max\left( {R_{\%\quad{diff}\quad 3},G_{\%\quad{diff}\quad 3},B_{\%\quad{diff}\quad 3}} \right)}}{{nB}_{\%\quad{diff}\quad 3} = \frac{B_{\%\quad{diff}\quad 3}}{\max\left( {R_{\%\quad{diff}\quad 3},G_{\%\quad{diff}\quad 3},B_{\%\quad{diff}\quad 3}} \right)}}} & (22)\end{matrix}$

The next p7 matrix corresponding to the difference is established atstep 136. The next p7 matrix may be calculated according to Equation(23): $\begin{matrix}{{p\quad 7} = {{p7}_{i}{column}\quad 7*\begin{pmatrix}{nR}_{\%\quad{diff}\quad 3} \\{nG}_{\%\quad{diff}\quad 3} \\{nB}_{\%\quad{diff}\quad 3}\end{pmatrix}}} & (23)\end{matrix}$After determining the next p7 matrix, the method terminates.

The illustrated embodiment describes estimating adjustments to achieve atarget white point value. Any target color value, however, can be used.According to one embodiment, a target primary value may be given, andthe method may estimate adjustments to achieve the target primary value.According to another embodiment, the duty cycle sequence changes may notbe used. Instead, major adjustments may be performed by increasingcurrent levels for one or more primaries. The p7 matrix may be used toprovide minor adjustments.

Modifications, additions, or omissions may be made to the method withoutdeparting from the scope of the invention. The method may include more,fewer, or other steps. Additionally, steps may be performed in anysuitable order without departing from the scope of the invention.

Certain embodiments of the invention may provide one or more technicaladvantages. A technical advantage of one embodiment may be that currentlevels and duty cycle sequences provided to a light source array aresynchronized in order to manage the color temperature or xy location ofthe array. The color management may yield an appropriate colortemperature or xy location while optimizing the lumens output of thelight source array.

While this disclosure has been described in terms of certain embodimentsand generally associated methods, alterations and permutations of theembodiments and methods will be apparent to those skilled in the art.Accordingly, the above description of example embodiments does notconstrain this disclosure. Other changes, substitutions, and alterationsare also possible without departing from the spirit and scope of thisdisclosure, as defined by the following claims.

1-20. (canceled)
 21. A method for providing color management,comprising: receiving color data; selecting a duty cycle sequence inaccordance with said received color data; and selecting a current levelin accordance with the duty cycle sequence, the one or more currentlevels being for one or more currents provided to a light source. 22.The method of claim 21 further comprising: establishing a target colorvalue.
 23. The method of claim 21, wherein selecting the duty cyclesequence further comprises: establishing a plurality of target valuescorresponding to a target color value; establishing a plurality of firstmeasured values from the color data; determining a first differencebetween the target values and the first measured values; and selecting aduty cycle sequence corresponding to the first difference.
 24. Themethod of claim 21, wherein selecting the duty cycle sequence furthercomprises: determining a candidate duty cycle sequence in accordancewith a target color value and the color data; and selecting an availableduty cycle sequence that is close to the candidate duty cycle sequence.25. The method of claim 21, wherein selecting the one or more currentlevels further comprises: establishing a plurality of target valuescorresponding to a target color value; establishing a plurality ofsecond measured values corresponding to the selected duty cyclesequence; determining a second difference between the target values andthe second measured values; and selecting one or more current levelscorresponding to the second difference.
 26. The method of claim 21,further comprising generating a color matrix by: establishing aplurality of target values corresponding to a target color value;establishing a plurality of third measured values corresponding to theselected duty cycle sequence and the selected one or more currentlevels; determining a third difference between the target values and thethird measured values; and generating the color matrix from the thirddifference.
 27. The method of claim 21, wherein the color data comprise:a plurality of internal measurements, an internal measurement measuredat a portion of an optical path prior to a screen with the image iscreated; and a plurality of external measurements, an externalmeasurement measured at a portion of the optical path posterior to thescreen.
 28. The method of claim 21, wherein the color data furthercomprises: receiving the plurality of measurements comprising aplurality of internal measurements and a plurality of externalmeasurements; and scaling the internal measurements and the externalmeasurements.
 29. The method of claim 21, further comprising providingcontrol information, the control information instructing a light sourcedriver to provide the one or more currents to the light source at theone or more selected current levels.
 30. The method of claim 21, furthercomprising providing control information, the control informationinstructing the light source to operate according to the selected dutycycle sequence.